_What are the solids?_

Fat, sugar, proteids, and salts.

_What is the fat?_

The cream.

_What is the sugar?_

It is lactose, or milk sugar.

_What are the proteids?_

The curd of the milk.

_Are all these elements necessary?_

Yes; we cannot expect to rear a healthy infant unless they are all in
his food.

_Of what use is the fat?_

It is needed for the growth of the bones, the nerves, the fat of the
body, and the production of heat.

_Of what use is the sugar?_

It is needed for the production of heat, and to make fat in the body.